Novel reaction products and organic compositions containing same



positions enhanced stability. Another object is to provide novel United States Patent 3,351,554 NOVEL REACTZGN PRUDUCTS AND URGANIC COMPOSETIUNS CONTAINHNG SAME Herbert Myers, Barrington, and William F. Olszewski, Cherry Hill, NJ, assignors to Mobil Gil Corporation, a corporation of New York No Drawing. Filed Jan. 25, 1966, Ser. No. 522,368

15 Claims. (Cl. 252--46.6)

This invention relates to novel reaction products and in particular this invention relates to novel phosphorussulfur compounds and organic compositions containing the same.

It is well known that many industrial liquids and solids, either of organic or inorganic nature, when used in industrial applications, such as lubricants and greases, plastics, coatings, insulation, power transmission fluids,

.and the like, are subjected to considerable deteriorative attack by surrounding conditions. High temperature oxidation is one of the major causes of the breakdown, particularly of organic materials. The material may become or abrading actions occur between metal surfaces, a film or coating of lubricant is required to form over these metal surfaces if successful lubrication is to be obtained. Quite often, particularly in todays modern engines, this protective layer becomes disrupted and the metal may become scorched thereby interfering with the required movement.

In order to aid the preponderant material or base medium in performing as desired, additives are blended therein to resist each deteriorative force acting upon that material. Rarely is one additive suficient to provide all of the required assistance needed. The discovery therefore of new additives providing improved individual properties or possessing a number of diiferent properties is greatly desired.

It is therefore a major object of this invention to provide novel compounds which possess oxidation resisting properties. A further object is to provide organic comcontaining these novel additives which have lubricant compositions which possess both oxidation resistance and load-carrying ability. These and other objects will be apparent from the following description.

It has now been discovered that organic compositions normally susceptible to the breakdown caused by oxidation and extreme pressure may have improved resistance to such breakdown by the presence therein of a minor amount of a product prepared by reacting 1) a phosphorus-sulfur compound of the structure wherein R, R and R" may each be alkyl, cyclolkyl, aralkyl, aryl, alkaryl, and substituted derivatives thereof, wherein the substituents may be attached to either alkyl or aryl groups and may contain atoms of nitrogen, oxygen, sulfur and halogen and wherein these R groups may be the same or different; and each X is either sulfur or oxygen or both in the same molecule, at least one X being sulfur,

(2) and an inorganic phosphorus-containing acid.

3,351,554 Patented Nov. 7, 1967 Preferably the phosphoroussulfur compound is a dithioite, wherein tow of the X atoms are sulfur.

We have now discovered that these reaction products provide excellent antioxidant properties to organic media in general. They also permit lubricant compositions containing these products to support greater loads, a particularly important characteristic in lubricant film-forming applications. Although phosphorus-sulfur compounds have been used as lubricant additives in the past, for either property, the reaction products prepared in accordance with this invention show an unexpectedly improved response in both these characteristics.

The compounds of this invention may be prepared simply by mixing the phosphorussulfur reactant with the phosphorus-containing acid, using a mole ratio of 1:2 to 3:1 of acid to phosphorus-sulfur reactant and heating the mixture to a temperature in the range of from approximately 50 to C., for a period of from about 30 minutes to about 10 hours. The progress of the reaction may be visually determined by the solubilization of the inorganic phosphorus acid into the reaction mixture. The inorganic phosphorus-containing acids used in this invention are generally insoluble in the phosophorussulfur compound. As the reaction proceeds, solubilization occurs gradually. The final product of this invention are usually clear, homogeneous fluids. It is not clearly determined the manner in which chemical bonding occurs and hence the final product cannot be identified with certainly. However, from spectroscopic evidence it is believed that the reaction product may be a mixture consisting predominantly of (R0) (RS)P(O)H and (RS) P(O)H type phosphonates.

The phosphorus-sulfur reactant of this invention may be the organic derivatives of mono-, di-, and trithioites I of the corresponding phosphorus ester. The phosphorussulfur reactant may be prepared by the known reaction between a phosphorus halide, an alcohol, and a mercaptan, in which the RO of the alcohol and the RS of the mercaptan replaces the halogen atoms. The replacement reactions may be performed stepwise or else the reactants may be added together.

Preferably phosphorodithioites are employed. Thus, for example, reacting phosphorous trichloride and ethyl alcohol in a 1:1 mole ratio, and then reacting two moles of ethyl mercaptan with the resulting monoethyl phosphorodichloridite in the presence of a base yields triethyl phosphorodithioite. Alternatively the mercaptan may be reacted with the phosphorus halide first, using the desired number of moles, and the remaining halogen is finally replaced by the RO-- portion of an alcohol. The monothioite is is prepared by reversing the above mole ratios. With regard to the trithioite, reaction of threee moles of, for example, ethyl mercaptan with phosphorus trichloride will yield triethylphosphorotrithioite.

Broadly, it is seen that these compounds are derived from a trivalent phosphorus compound reacted with an alcohol or thioalcohol, wherein the organic portion of the alcohol consists of aliphatic and aromatic compounds. Such organic groups include the alkyl radicals, such as ethyl, propyl, butyl, amyl, hexyl, cyclohexyl, octyl, ethylhexyl, decyl and other alkyl groups. Although the number of carbon atoms may be considerably higher, it is preferred to employ phosphorus-sulfur compounds having R groups of from 1 to about 20 carbon atoms. Attached to these alkyl radicals may be other substituents containing nitrogen, oxygen, sulfur and halogen atoms, such as amino, nitro, hydroxy, sulfo, alkoxy, chloro, bromo, and the like. The alkyl groups may also have aryl functions attached thereto, such as in the benzyl radical. The R groups may be aromatic, including phenyl and napthyl, and these groups may also have substituents attached thereto, such as other alkyl groups, as in tolyl, aryl groups as in diphenyl, and the non-hydrocarbyl substituents recited above containing nitrogen, oxygen, sulfur and halogen atoms. As above, the aromatic R groups may have no upper limit of the number of carbon atoms, however, the referred range is from 1 to about 20.

With regard to the phosphorus-containing acid either trivalent or pentavalent inorganic phosphorus acids may be used. Such acids include H PO H PO H P O I-I PO HPO and H P O The most preferred of these acids is phosphorous acid in any of the three isomeric forms. Phosphoric acid may also be used.

The reaction may be conducted in any suitable reaction vessel at a temperature ranging from about 50 to about 150 C. and preferably from about 70 to about 90 C. The mole ratio of the reactants, as indicated earlier, may range from 1:2 to 3:1 of acid to phosphorus-sulfur reactant. The reaction is generally complete in from 1 to 6 hours.

The novel compounds of this invention may be added to various organic base media, such as mineral oil lubricants, synthetic lubricants, including diester, triester and tetraester base fluids, olefin polymer fluids, alkylene oxide fluids, silicone polymer fluids and the like. These additives may be admixed with thickeners in such above fluids for use in solid lubricants, such as greases. The compounds of-this invention may also find utility in plastic compositions, both for structural and coating purposes. The preferred utility for these compounds are additives in lubricating oils, both petroleum and synthetic. They may be present in the total composition at concentrations ranging from 0.005% to about 10% by weight.

The following examples are provided to better illustrate the nature of this invention and are not intended to be a limitation of the scope thereof.

Example 1 Into a flask equipped with a stirrer, condenser and thermometer were added 155 grams (0.78 mole) of triethyl phosphorodithioite and 33 grams (0.39 mole) of ortho phosphorous acid in the form of 97% flake. The phosphorous acid was insoluble in the phosphorus-sulfur reactant at the start. The reaction mixture was heated slowly under agitation to a temperature in the range of 80 to 85 C. whereat the acid became completely dissolved in the mixture. The mixture was stirred at a temperature in this range for 3 hours. The resulting clear colorless solution was thereafter topped at 80 C. at 0.01 mm. Hg pressure, but no distillate was obtained.

Product Analysis: Phosphorus, 21.1%; Sulfur, 24.4%.

Example 2 Following the reaction procedure of Example 1, 8,8- di-n-propyl-O-n-butyl phosphorodithioite was reacted with phosphorous acid in a 1:2 mole ratio of acid to phosphorus-sulfur compound. The product had the following analysis:

Product Analysis: Phosphorus, 15.7%; Sulfur, 20.7%.

Example 3 Following the reaction procedure of Example 1, tri-nbutyl phosphorodithioite was reacted with phosphorous acid in a 1:2 mole ratio of acid to phosphorus-sulfur compound.

Product Analysis: Phosphorus, 14.4%; Sulfur, 19.5%.

Example 4 Following the reaction procedure of Example 1, S,S diethyl-O-(Z-ethylhexyl)phosphorodithioite was reacted with phosphorous acid in a 1:2 mole ratio of acid to phosphorus sulfur compound.

Product Analysis: Phosphorus, 14.2%; Sulfur, 18.5%.

Example 5 Following the reaction procedure of Example 1, 67 grams (0.17 mole) of S,S-di-(2-ethylhexyl)-O-n-buty1 phosphorodithioite was reacted with 7.6 grams (0.9 mole) 4 of phosphorous acid, and the product was topped as earlier described.

Product Analysis: Phosphorus, 10.7%; Sulfur, 14.6%.

Example 6 Following the reaction procedure of Example 1, 8,5- diphenyl-O-n-butyl phosphorodithioite was reacted with phosphorous acid in a 1:2 mole ratio of acid to phosphorus-sulfur compound. The product of this reaction was a white solid.

Product Analysis: Phosphorus, 12.3%; Sulfur, 17.4%.

Example 7 Following the reaction procedure of Example 1, S,S-di n-butyl-O-phenyl phosphorodithioite was reacted with phosphorous acid in a 1:2 mole ratio of acid to phosphorus-sulfur compound.

Product Analysis: Phosphorus, 13.4%; Sulfur, 18.0%.

Example 8 Following the reaction procedure of Example 1, tri-nbutyl phosphorodithioite was reacted with phosphorous acid in a 1:2 mole ratio of acid to phosphorus-sulfur compound.

Product Analysis: Phosphorus, 14.7%; Sulfur, 11.5%.

Example 9 Following the reaction procedure of Example 1, tri-nbutyl phosphorotrithioite was reacted in an Erlenmeyer flask equipped with a magnetic stirrer with phosphorous acid in a 1:2 mole ratio of acid to phosphorus-sulfur compound. The reaction product contained unreacted phosphorous acid.

Product Analysis: Phosphorus, 10.7%; Sulfur, 29.9%.

Theoretical for (C H S)3P. Phosphorus, 10.0%; Sul fur, 32.1%.

Example 10 Tri-n-butyl phosphorotrithioite and 97% flake phosphorous acid in amounts equivalent to a 1:2 mole ratio of acid to phosphorus-sulfur compound were heated for 24 hours in an Erlenmeyer flask at a temperature in the range of to 90 C. The crude product was a dark brown, hazy mixture. Upon filtering this mixture through diatomaceous earth filter aid a clear, amber colored product was obtained.

Product Analysis: Phosphorus, 14.8%; Sulfur, 24.4%.

Example 11 In a manner following Example 1, tri-n-butyl phosphorodithioite was reacted with the phosphorous acid using a 1:1 mole ratio of acid to phosphorus-sulfur compound. The reaction mixture was heated for 3 hours at a temperature in the range of 80 to C. A clear, colorless product was obtained.

Product Analysis: Phosphorus, 17.8%; Sulfur, 14.0%.

Example 12 In a manner following Example 1, tri-n-butyl phosphorodithioite was reacted with the phosphorous acid in this case using a 2:1 mole ratio of acid to phosphorussulfur compound. The reaction mixture was heated for 4 hours at a temperature in the range of 80 to 85 C. A clear, colorless product was obtained.

Product Analysis: Phosphorus, 21.5%; Sulfur, 13.0%.

Example 13 Example 14 In a manner following the procedure of Example 9, 129 grams (0.51 mole) of S,S-di-n-propyl-O-n-butyl phosphorodithioite was reacted with 30 grams (0.26 mole) of 85% phosphoric acid.

Product Analysis: Phosphorus, 16.4%; Sulfur, 17.1%.

EVALUATION OF PRODUCT In order to illustrate the utility of the reaction products of this invention formed by reacting organic phosphorussulfur compounds with phosphorus-containing acid a representative number of those prepared in the above examples were added to lubricating oils for evaluation both as antioxidants and as extreme pressure agents.

OXIDATION STABILITY TEST In this test, 25 cc. of the oil sample containing the test additive is subjected to oxidation by passing a stream of dry air therethrough at a rate of litersper hour at a temperature of about 324 F. for 24 hours. Immersed in the oil sample are metals known to catalyze oxidation. The metals are (a) 15.6 sq. in. of sand-blasted iron wire, (b) 0.78 sq. in. of polished copper wire, (c) 0.87 sq. in. of polished aluminum wire, and (d) 0.167 sq. in. of polished lead surface.

The effect of oxidation, as is well known, is to acidity the test oil or its components; in other words, the neutralization number of the oil increases. The additive is rated in the test according to the minimum concentration of phosphorus required to keep the acidity of the oxidized oil below a neutralization number of 2.0. Thus the lower the required concentration of phosphorus the more effective the additive. Comparative data are reported for the corresponding phosphorus-sulfur compounds which had not been reacted with the phosphorus-containing acid. The inorganic phosphorus acids being insoluble in oil cannot be readily evaluated. Hence results of such tests are not similarly reported. However, the amounts which may be dissolved in oil have been found to provide little or no antioxidation protection. The base oil used for this test is an SAE 10 solvent-refined Mid-Continent oil. The results are reported in Table 1.

Table 1 Minimum Percent Product: Phosphorus (D-C3H7S)2(I1-C4H9O)P over 0.37 Example 2 0.12 Example 14 0.25 (n-C H S) (n-C H O)P over 0.33 Example 3 under 0.08 Example 13 0.20

[CH (CH CH(C H )CH O]P over 0.33 Example 4 0.13

LOAD-CARRYING TEST The load-carrying capacity of a lubricant is measured under high speed shock conditions. The oil sample is placed in an SAE 1000 test machine as a lubricant for 2 steel test rings which are rotated against each other at diiferent speeds. Such rotation produces a combination of rolling and sliding actions. As rotation proceeds, the load holding the rings together is gradually increased by mechanical means until either the maximum load of the machine load is reached or until the rings seize, or fail to rotate. The maximum measurable loading for the machine used in this test is 460 lbs. The results are reported in pounds at seizure. Comparative data are also reported for the corresponding phosphorus-sulfur compound from which the additives of this invention were synthesized. The concen tration of the additive in the oil sample is sufiicient to provide 0.4% of phosphorus in the total composition. The base oil used was an SAE 90 solvent-refined Mid-Continent oil. The results are reported in Table 2.

Example 5 over 460 It is clear from the above results in both types of tests that the products of this invention have improved multifunctional properties when compared with the phosphorus-sulfur precursor reactant. Since the phosphoruscontaining acids alone provide no additional protection and since the results for both the products of this invention and for the comparative compound are based on the percent phosphorus present in the total composition, it must be concluded that the improvement obtained is derived from the novelty of the structure or composition of these reaction products, not from the extra proportion of any one element or group of elements.

The additives of this invention may be introduced into any organic composition which is susceptible to breakdown under oxidizing or mechanical stresses acting upon the composition. Not only lubricating oils, both natural and synthetic, are contemplated herein, but many other compositions requiring such protection. are applicable. Other additives may also be present in the composition and these include auxiliary antioxidants and load-carrying agents, detergents, pour point depressants, viscosity control agents, thickeners, pigments and the like.

Although this invention has been explained and illustrated with the aid of specific examples it is not intended to limit the scope of the invention except as appearing in the following claims.

We claim:

1. As a novel composition of matter the reaction product of a reaction between (1) a phosphorus-sulfur compound of the structure wherein R, R and R" may each be individually selected from the group consisting of alkyl, aralkyl, aryl, alkaryl, cycloalkyl and substituted derivatives thereof wherein such substituents contain atoms of nitrogen, oxygen, sulfur and halogen and each X atom is selected from the group consisting of sulfur and oxygen, wherein at least one X is sulfur and (2) an inorganic phosphorus-containing acid selected from the group consisting of phosphorus acid and phosphoric acid.

2. The composition of matter of claim 1 wherein the phosphorus-containing acid is a phosphorus acid.

3. The composition of matter of claim 2 wherein the phosphorus-containing acid is a phosphoric acid.

4. The composition of matter of claim 2 wherein the number of carbon atoms in the R, R and R" groups is from 1 to about 20.

5. The composition of matter of claim 1 wherein two of the X atoms are sulfur.

6. The composition of matter of claim 1 wherein the R groups are alkyl.

7. The composition of matter of claim 1 wherein the R groups are a mixture of alkyl and aromatic radicals.

8. The composition of matter of claim 1 wherein the phosphorus-sulfur compound is S,S-di-n-butyl-O-n-butyl phosphorodithioite.

9. The composition of matter of claim 1 wherein the R groups are tri-n-butyl radicals.

10. The composition of matter of claim 1 wherein the R groups are S,S-di-n-propyl-O-n-butyl radicals.

11. An organic composition comprising a preponderant amount of an organic base medium susceptible to oxidation deterioration and extreme pressure failure and a minor amount sufiicicnt to provide stabilization thereto of the composition of matter of claim 1.

12. The composition of claim 11 wherein the preponderant base medium is a lubricating oil.

13. The composition of claim 12 wherein the said composition of matter is the reaction product of S,S-di-npropyl-O-n-butyl phosphorodithioite and phosphorous acid.

14. The composition of claim 12 wherein the said composition of matter is the reaction product of tri-n-butyl phosphorodithioite and phosphorous acid.

15. The composition of claim 12 wherein the said composition of matter is the reaction product of S,S-di(2- v s ethylhexyl)-O-n-butyl phosphorodithioite and phosphorous acid.

References Cited UNITED STATES PATENTS 2,191,996 2/1940 Shoemaker et al. 25246.6 2,242,260 5/1941 Prutton 252-466 2,285,953 6/1942 Downing et al 25246.6 2,290,859 7/1942 Burk et al. 25246.6 2,834,797 5/1958 Chadwick 260-967 2,984,680 5/1961 Walsh 260-967 3,019,249 1/ 1962 Gunderloy 2 6O'-967 3,145,176 8/1964 Knapp et al 252-46.6

FOREIGN PATENTS 462,125 12/1949 Canada.

DANIEL E. \VYMAN, Primary Examiner.

L. G. XIARHOS, Assistant Examiner. 

1. AS A NOVEL COMPOSITION OF MATTER THE REACTION PRODUCT OF A REACTION BETWEEN (1) A PHOSPHORUS-SULFUR COMPOUND OF THE STRUCTURE
 11. AN ORGANIC COMPOSITION COMPRISING A PREPONDERANT AMOUNT OF AN ORGANIC BASE MEDIUM SUSCEPTIBLE TO OXIDATION DETERIORATION AND EXTREME PRESSURE FAILURE AND A MINOR AMOUNT SUFFICIENT TO PROVIDE STABILIZATION THERETO OF THE COMPOSITION OF MATTER OF CLAIM
 1. 